Conformal lining layers for damascene metallization

Abstract

Method and structures are provided for conformal lining of dual damascene structures in integrated circuits. Trenches and contact vias are formed in insulating layers. The trenches and vias are exposed to alternating chemistries to form monolayers of a desired lining material. Exemplary process flows include alternately pulsed metal halide and ammonia gases injected into a constant carrier flow. Self-terminated metal layers are thus reacted with nitrogen. Near perfect step coverage allows minimal thickness for a diffusion barrier function, thereby maximizing the volume of a subsequent filling metal for any given trench and via dimensions.

1. A metallization process, comprising:
 forming an opening in a porous low k dielectric material above a semiconductor substrate in a process chamber to expose at least part of an underlying conductive element; 
 depositing no more than about one monolayer of a tantalum-containing species on surfaces of the opening; 
 reacting the no more than about one monolayer with a reducer; and 
 forming a lining layer by reacting a reactant species with the no more than about one monolayer after reacting the no more than about one monolayer with the reducer and before introducing any other reactants into the reaction chamber, wherein the lining layer conformally lines the opening, including the exposed part of the underlying conductive element. 
 
     
     
       2. The method of  claim 1 , wherein the reactant species is a non-radical species. 
     
     
       3. The process of  claim 2 , wherein the reactant species is a nitrogen precursor. 
     
     
       4. The process of  claim 3 , wherein the reactant species is ammonia. 
     
     
       5. The method of  claim 1 , wherein depositing the no more than about one monolayer comprises:
 introducing a tantalum precursor into the process chamber; and 
 removing the tantalum precursor from the process chamber before reacting the no more than about one monolayer with the reducer. 
 
     
     
       6. The process of  claim 1 , wherein the tantalum precursor comprises an organic ligand. 
     
     
       7. The process of  claim 6 , wherein the tantalum precursor is pentakis(dimethylamino)tantalum. 
     
     
       8. The process of  claim 1 , wherein the tantalum precursor comprises a halide ligand. 
     
     
       9. The process of  claim 8 , wherein the tantalum precursor is TaCl 5 . 
     
     
       10. The process of  claim 1 , wherein the reducer is triethyl boron. 
     
     
       11. The process of  claim 1 , wherein the lining layer has a step coverage of greater than about 90%. 
     
     
       12. The process of  claim 1 , wherein the opening has a width of less than about 0.35 μm. 
     
     
       13. The method of  claim 1 , wherein depositing no more than about one monolayer of a tantalum-containing species on surfaces of the opening comprises depositing directly on surfaces of the opening in the porous low k dielectric material. 
     
     
       14. The method of  claim 1 , wherein forming a lining layer comprises forming an adhesion layer prior to depositing a barrier layer thereover. 
     
     
       15. The method of  claim 1 , further comprising providing a surface termination of the exposed part of the underlying conductive element prior to depositing no more than one monolayer of the tantalum-containing species. 
     
     
       16. The method of  claim 15 , wherein providing the surface termination comprises performing an ammonia treatment.